offset - Integer used in the name stack to identify the part of the component.

maxZ - Stores the z coordinate of the part with maximum z coordinate in the actual picking.
It has to be set if the part with the current offset has greater z coordinate than the stored one.
Example to compute: int aIdx = GeomCalc.newVector( picked.x(), picked.y(), picked.z() );GeomCalc.multVectorWithMatrix(aIdx, modelview);
z coordinate: maxZ[0] = GeomCalc.getZ(aIdx)